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Assembly-driven activation of the AIM2 foreign-dsDNA sensor provides a polymerization template for downstream ASC.

Morrone SR, Matyszewski M, Yu X, Delannoy M, Egelman EH, Sohn J - Nat Commun (2015)

Bottom Line: The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers.The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC.Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine Baltimore, Maryland 21205, USA.

ABSTRACT
AIM2 recognizes foreign dsDNA and assembles into the inflammasome, a filamentous supramolecular signalling platform required to launch innate immune responses. We show here that the pyrin domain of AIM2 (AIM2(PYD)) drives both filament formation and dsDNA binding. In addition, the dsDNA-binding domain of AIM2 also oligomerizes and assists in filament formation. The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers. The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC. Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

No MeSH data available.


Related in: MedlinePlus

Mutagenesis studies to test the role of AIM2PYD in dsDNA binding.(a) The sequence alignment of ALRs. The mutated side chains are indicated in red. (b) The crystal structure of AIM2PYD (PDB ID: 3VD8). The mutated side chains are shown as spheres. The amino acids indicated in the parentheses are the equivalent IFI16 residues. (c) Binding of FAM-dsDNA72 (1.5 nM) by various AIM2FL PYD mutants were tested at 400 mM KCl. The determined KD values are listed in Supplementary Table 2.
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f3: Mutagenesis studies to test the role of AIM2PYD in dsDNA binding.(a) The sequence alignment of ALRs. The mutated side chains are indicated in red. (b) The crystal structure of AIM2PYD (PDB ID: 3VD8). The mutated side chains are shown as spheres. The amino acids indicated in the parentheses are the equivalent IFI16 residues. (c) Binding of FAM-dsDNA72 (1.5 nM) by various AIM2FL PYD mutants were tested at 400 mM KCl. The determined KD values are listed in Supplementary Table 2.

Mentions: Previously, we found that several highly conserved surface side chains of IFI16 mediate its oligomerization-driven dsDNA-binding mechanism23 (Fig. 3a). For AIM2, several equivalently positioned surface side chains mediate the auto-oligomerization of isolated AIM2PYDin vivo34 and interaction with ASCPYDin vitro7 (for example, Leu10, Leu11 and Phe27 in Fig. 3b). However, whether these side chains have any role in dsDNA binding remains unknown. To further test the positive role of AIM2PYD in dsDNA binding, we then generated a panel of surface mutants based on our study of IFI16 (ref. 23) and sequence conservation (Fig. 3a,b; none of these side chains are implicated in the alleged autoinhibition of AIM2 (refs 32, 33), see also below). Almost all of these PYD mutants significantly disrupted the dsDNA-binding activity of AIM2FL (Fig. 3c), supporting that oligomerization of PYD plays a major positive function in dsDNA binding.


Assembly-driven activation of the AIM2 foreign-dsDNA sensor provides a polymerization template for downstream ASC.

Morrone SR, Matyszewski M, Yu X, Delannoy M, Egelman EH, Sohn J - Nat Commun (2015)

Mutagenesis studies to test the role of AIM2PYD in dsDNA binding.(a) The sequence alignment of ALRs. The mutated side chains are indicated in red. (b) The crystal structure of AIM2PYD (PDB ID: 3VD8). The mutated side chains are shown as spheres. The amino acids indicated in the parentheses are the equivalent IFI16 residues. (c) Binding of FAM-dsDNA72 (1.5 nM) by various AIM2FL PYD mutants were tested at 400 mM KCl. The determined KD values are listed in Supplementary Table 2.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4525163&req=5

f3: Mutagenesis studies to test the role of AIM2PYD in dsDNA binding.(a) The sequence alignment of ALRs. The mutated side chains are indicated in red. (b) The crystal structure of AIM2PYD (PDB ID: 3VD8). The mutated side chains are shown as spheres. The amino acids indicated in the parentheses are the equivalent IFI16 residues. (c) Binding of FAM-dsDNA72 (1.5 nM) by various AIM2FL PYD mutants were tested at 400 mM KCl. The determined KD values are listed in Supplementary Table 2.
Mentions: Previously, we found that several highly conserved surface side chains of IFI16 mediate its oligomerization-driven dsDNA-binding mechanism23 (Fig. 3a). For AIM2, several equivalently positioned surface side chains mediate the auto-oligomerization of isolated AIM2PYDin vivo34 and interaction with ASCPYDin vitro7 (for example, Leu10, Leu11 and Phe27 in Fig. 3b). However, whether these side chains have any role in dsDNA binding remains unknown. To further test the positive role of AIM2PYD in dsDNA binding, we then generated a panel of surface mutants based on our study of IFI16 (ref. 23) and sequence conservation (Fig. 3a,b; none of these side chains are implicated in the alleged autoinhibition of AIM2 (refs 32, 33), see also below). Almost all of these PYD mutants significantly disrupted the dsDNA-binding activity of AIM2FL (Fig. 3c), supporting that oligomerization of PYD plays a major positive function in dsDNA binding.

Bottom Line: The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers.The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC.Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

View Article: PubMed Central - PubMed

Affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine Baltimore, Maryland 21205, USA.

ABSTRACT
AIM2 recognizes foreign dsDNA and assembles into the inflammasome, a filamentous supramolecular signalling platform required to launch innate immune responses. We show here that the pyrin domain of AIM2 (AIM2(PYD)) drives both filament formation and dsDNA binding. In addition, the dsDNA-binding domain of AIM2 also oligomerizes and assists in filament formation. The ability to oligomerize is critical for binding dsDNA, and in turn permits the size of dsDNA to regulate the assembly of the AIM2 polymers. The AIM2(PYD) oligomers define the filamentous structure, and the helical symmetry of the AIM2(PYD) filament is consistent with the filament assembled by the PYD of the downstream adaptor ASC. Our results suggest that the role of AIM2(PYD) is not autoinhibitory, but generating a structural template by coupling ligand binding and oligomerization is a key signal transduction mechanism in the AIM2 inflammasome.

No MeSH data available.


Related in: MedlinePlus